The present invention relates to a process for separating an organic material from a composition comprising the organic material intermixed with particulate solids. The invention is particularly suitable for separating organic material from particulate solid waste and particulate hazardous waste. It is also suitable for treating waste streams containing catalyst fines (e.g. decanter oil streams from fluid catalytic cracking units), oil contaminated drill cuttings, contaminated soil, steel mill scale, bleaching clay and the like.
Refinery sludges typically are mixtures of hydrocarbon oils, heavy residual hydrocarbons including asphaltenes, water and particulate solids. These sludges are produced from a number of refinery units, including various standard waste water treatment separators. The sludges often contain substances such as benzene, toluene, xylene, chrysene, etc. which are listed as hazardous materials by the Environmental Protection Agency (EPA). Typically, refinery sludges have in the past been disposed of by land filling and land farming techniques. However, because of environmental considerations, land disposal or land filling has recently become more difficult and much more expensive. Therefore, alternatives to conventional land filling and land farming techniques have been examined for hazardous waste removal. U.S. Pat. Nos. 4,341,619; 4,434,028 and the final report for EPA Contract No. 68-02-3924 are all concerned with various techniques for recovering carbonaceous or hydrocarbon materials from various hazardous waste streams.
U.S. Ser. No. 906,727 assigned to the assignee of the present application, discloses an alternative to these techniques for producing an environmentally suitable waste stream. The invention of the above-identified application provides for a process of separating an organic material from a composition comprising the organic material intermixed with particulate solids, comprising advancing a light hydrocarbon fluid through said particulate solids at an effective rate to drive the organic material from the particulate solids. In addition, the technique disclosed involves a multi-step procedure involving utilizing a light hydrocarbon material to initially extract the organic material from the particulate solids followed by using a higher molecular weight hydrocarbon to further capture the undesirable residual organic material from the particulate solids followed by a third step of extracting with a second light hydrocarbon material to further separate the residual higher molecular weight hydrocarbon fluids from the particulate solids. The present invention is directed to an improvement in the procedure disclosed in Ser. No. 906,727.